It is known that the serum of numerous subjects who are carriers of Australia antigen (HB.sub.s Ag) contains another antigen which has been called hepatitis B e antigen (HB.sub.e Ag). See Magnius et al., Acta. Path. Microbiol. Scand., Section B, 80, 335-337 (1972). Specimens of HB.sub.e Ag are to be found at the Department of Virology, Statens Bakteriologeska Laboratorium, Stockholm and at the Liver Study Unit of Yale University, New Haven, Conn., U.S.A.
HB.sub.e Ag is an antigenic complex of a group of soluble proteins (called e.sub.1, e.sub.2, etc.) which are normally found in acute hepatitis B cases as well as in the serum of chronic carrier cases of HB.sub.s Ag. HB.sub.e Ag is also found in hemodialysed or in immunode-pressed subjects or in subjects suffering from Down's syndrome. These various antigen determinants are immunologically distinct from HB.sub.s Ag. It has been found that the administration of HB.sub.e Ag elicits an immunological response with formation of hepatitis B e antibody (HB.sub.e Ab).
While HB.sub.e Ag is present in biological fluid of individuals who have been infected with hepatitis B, the HB.sub.e Ag frequently is present in concentration too low to be detected by present assays. As a result the fluid is considered negative for HB.sub.e Ag and no attempt to recover e antigen therefrom is made.
It is also known that the biological fluid of healthy, chronic carriers of HB.sub.s Ag, in which the titers of HB.sub.s Ag are relatively low, is positive for hepatitis B e antibody (HB.sub.e Ab). As presently available assays for this antibody are relatively insensitive, most of these fluids are considered negative for this antibody and recovery of the antibody is not attempted.